The present invention relates to primers used in conjunction with neoprene adhesives to adhere roofing materials and more particularly to primer mixtures of thermoplastic block copolymer rubber, halogenated butyl rubber and aromatic hydrocarbon reinforcing resin.
Roofing materials useful for covering large roof areas are customarily prepared in wide sheets for efficient installation. These wide sheets must be overlapped and spliced together when the roofing sheets are installed to provide uniform surfaces. Overlap splicing is often done under extreme weather conditions and the adhered sections must continue to withstand severe weather at extremes of cold and hot temperatures for many years. Roofing materials are available in black and in various colors including white.
Customarily roofing materials, made from plastic, rubber or ethylene propylene diene monomer (EPDM), have been spliced together on site with neoprene (polychloroprene) based contact adhesives. A well known treatise, the Handbook of Adhesives edited by Irving Skeist, published by Van Nostrand Reinhold Company, 1977 edition, at page 880, recommends the use of neoprene based adhesives on EPDM substrates.
EPDM membranes are a very popular form of single ply roofing. Although black EPDM membrane is the most widely used, white EPDM membrane is gaining in popularity. Often they are treated with talc, mica, or cellulosic powders to improve processing and handling of the finished membrane. Splice adhesives adhere poorly to these treated surfaces.
It is desirable to use a primer on the EPDM membrane substrate before applying the neoprene based adhesives. The strength and durability of the final bond between adhesive and substrate depend greatly on the strength of the bond created by the primer. Conventional commercial primers typically provide poor bond strengths of about three pounds/inch when used with neoprene based adhesives.
These conventional commercial primers frequently contain environmentally undesirable ingredients such as lead salts and free isocyanates. When black conventional primers are used on white EPDM roofing membranes special techniques are necessary to prevent the black color of the primer from showing on the final adhered surface.